linux-kernel - [PATCH 4.19 121/293] blk-zoned: allow BLKREPORTZONE without CAP_SYS

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Date:   Mon, 20 Sep 2021 18:41:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Niklas Cassel <niklas.cassel@....com>,
        Damien Le Moal <damien.lemoal@....com>,
        Aravind Ramesh <aravind.ramesh@....com>,
        Adam Manzanares <a.manzanares@...sung.com>,
        Himanshu Madhani <himanshu.madhani@...cle.com>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.19 121/293] blk-zoned: allow BLKREPORTZONE without CAP_SYS_ADMIN

From: Niklas Cassel <niklas.cassel@....com>

commit 4d643b66089591b4769bcdb6fd1bfeff2fe301b8 upstream.

A user space process should not need the CAP_SYS_ADMIN capability set
in order to perform a BLKREPORTZONE ioctl.

Getting the zone report is required in order to get the write pointer.
Neither read() nor write() requires CAP_SYS_ADMIN, so it is reasonable
that a user space process that can read/write from/to the device, also
can get the write pointer. (Since e.g. writes have to be at the write
pointer.)

Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
Signed-off-by: Niklas Cassel <niklas.cassel@....com>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Reviewed-by: Aravind Ramesh <aravind.ramesh@....com>
Reviewed-by: Adam Manzanares <a.manzanares@...sung.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@...cle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Cc: stable@...r.kernel.org # v4.10+
Link: https://lore.kernel.org/r/20210811110505.29649-3-Niklas.Cassel@wdc.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 block/blk-zoned.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -319,9 +319,6 @@ int blkdev_report_zones_ioctl(struct blo
 	if (!blk_queue_is_zoned(q))
 		return -ENOTTY;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
 	if (copy_from_user(&rep, argp, sizeof(struct blk_zone_report)))
 		return -EFAULT;